1. Field of the Invention
The present invention relates to the assisting of an airport craft (vehicle, aircraft) to comply with taxiing constraints. It more particularly pertains to the detection and the signalling, to an airport craft, of the local circulation constraints related to the situation of the craft in the ground traffic of an airport.
2. Description of the Related Art
Since the sizeable reduction in air accidents due to a collision with the ground of an aircraft that is still manoeuvring, so-called CFIT-type accidents (the acronym standing for the expression: “Controlled Flight Into Terrain”), obtained with TAWS ground collision prevention systems (the acronym standing for the expression: “Terrain Awareness and Warning System), the main cause of air accidents is now becoming airport collisions on the ground between aeroplanes or other craft.
The main reason for these ground traffic accidents in airports, commonly known by the expressions “Runway Incursion” or “Runway Intrusion”, is the unauthorized encroachment of a craft onto a traffic lane (runway, taxiway, parking area, etc.). Such unauthorized encroachments which inevitably give rise to risks of collision with possible aeroplanes taxiing or taking off or landing are, in essence, the consequence of a noncompliance (in large part through inattentiveness) with the taxiing authorizations provided by the airport or air traffic control authorities.
The continuous increase in air traffic and the growing complexity of the network of airport traffic lanes are favouring these risks of intrusion even more.
According to the rules currently in force, the taxiing of a craft on an airport is performed on request and by the commander of the craft, but according to the authorizations provided by the airport or air traffic control authorities in charge of ensuring the organized and safe circulation of ground movements. The commander of the craft taxies his craft freely within the framework of the authorizations obtained.
Hitherto, the surveillance of airport surface taxiing movements and of their compatibility with the authorizations granted has been performed visually by the airport or air traffic control authorities, very often with the aid of surveillance systems, based for the most part, on airport surface ground surveillance radars, and possibly supplemented in the last few years with multi-lateration ground systems using the data originating from onboard transponders.
On the basis of visual checking and of the position information provided by these airport surface ground surveillance systems, the airport or air traffic control authorities formulate, for the various craft, taxiing authorizations that are valid up to a so-called reporting point, where the craft must wait and obtain a new authorization to perform a new movement, doing so until it reaches its final destination.
The taxiing authorizations and their characteristics (route, compulsory reporting point) are very widely provided by speech (typically via a VHF radio channel). Hitherto, they have been taken into account mentally by the commander of the craft and rarely inserted into onboard systems.
Recently at a few airports and with a few airlines, these instructions may be provided to the aircraft by digital transmission by means of onboard equipment of the CPDLC type (the acronym standing for the expression: “Controller-Pilot Data Link Communications”) in the form of standardized messages such as a PDC message (the acronym standing for the expression: “PreDeparture Clearances”) via a VHF radio channel. The instructions are then displayed on an onboard screen (or even printed on board), but in general not inserted at the level of the other onboard systems. Such an insertion is nevertheless conceivable, at the very least manually, with the aid or otherwise of predefined lists of routes.
The reporting points marking the conclusions of the legs associated with the taxiing authorizations, also known by various names such as “Stop-bars” or “Holding points”, “taxiway holding positions”, “taxiway intersection markings”, etc., are systematically placed at the thresholds of the crossings of the runways and of the taxiways but they may also be placed elsewhere in the traffic lanes of an airport.
Taxiing being left to the free initiative of the commander of the craft up to the reporting point, noncompliance (principally through inattentiveness) with the reporting point or with the route assigned may give rise to the abovementioned risks of “Runway Incursion” or “Runway Intrusion”.
Hitherto, no operational system has been available on board an aircraft to aid the pilot to follow the route assigned to him by ground control and especially to signal to him any crossing of a compulsory reporting point that may or may not have been assigned to him (for example following a route error). Such functions are ensured only at the ground control level whereas they would be very useful on board a craft for assisting the commander of the craft to follow the routes corresponding to the taxiing authorizations.
The literature mentions various experiments conducted with a view to formulating onboard equipment facilitating the piloting of an aircraft during its taxiing on the surface of an airport especially in case of poor visibility. The article by Sharon Otero Beskenis et al., entitled “Integrated Display System For Low Visibility Landing and Surface Operations” published in July 1998 under the reference NASA/CR-1998-208446 describes an experiment with a Boeing B-757-type aircraft equipped with an HDD head-down display exhibiting a dropdown map of the airport pinpointing the aircraft on the traffic lanes of the airport by utilizing a geographical location fix delivered by a differential satellite positioning system and an electronic map of the airport, portraying the taxiing leg assigned to the aircraft by the airport traffic control authorities, the reporting points delimiting the taxiing authorizations as well as reporting points transmitted by a runway anti-intrusion ground system dubbed AMASS (the acronym standing for the expression: “Airport Movement Area Safety System”).
These conclusive experiments have had no immediate repercussion on account of the high level of equipment required for the ground installations of the airport. Since then, simpler systems have been proposed, rendering a less complete service but not necessitating particular equipment for the airport.
U.S. Pat. No. 6,606,563 describes an alert system charting, by GPS positioning, the position of an aircraft on an airport surface modelled in an electronic map, estimating the distance separating it from the runways and signalling to the pilot any approach to or encroachment onto a runway. This system which is a less secure variant of the AMASS system draws the pilot's attention to the fact that he is approaching or encroaching onto a runway but does not aid him when taxiing to follow the route assigned to him by the airport traffic control authorities.